alloy brake pads

[02gf74]

Alloy brake pads replacements are available for a number of makes/models: shimano, avid and formula.

They save approx 8 -10 g per pair but im wondering if they are a good idea. Al conducts heat better than steel and you do not want the heat going through the pads to the pistons and into the brake fluid.

Ive not experienced brake fade but would have thought it would happen sooner with alloy pads.

Just throwing the question to the engineering and physicist type bods out there, has there been any like for like tests on them?

 

[FluffyChicken]

Re:

No idea as i be not touched the devils work if decent brakes.

But surely the cooling is designed into the brake itself. So if you can get it away from the pad, assuming that keeping the pad cooler is a good thing*, then the design will get rid of it if it is needed and keep it away from any liquids which may be sensitive to it. Or of course pick a liquid that is not sensitive to it.

So I would conclude, if its designed well it'll not matter.

* I know on rim brakes they work better when they are warm, but not too warm.

 

[02gf74]

Not sure i follow that^^^^

I thought brakes stop better when warm - watch F1 and you see the drvers wanting to put heat into both tyres and brakes but that may be how they were designed to operate.

You want to keep heat away from the calliper, the the latest shimano ice brakes where tbe pads have cooling fins.

 

[FluffyChicken]

I was saying, it depends on how they are designed to operate.
They will be designed to work best at a specific range of temperatures.
Downhill, I would assume designed to work at a higher temperature.
General bimble to the shops at a low end of temperatures.

It's all in the design.

If the calliper is designed for the higher heat, you'll need heat in it to have everything expand to it's correct position and the lubricant to work. BUT I really doubt we are talking of F1 or even car temperatures here normally.

What you don't want is a build up of heat that you cannot get rid of, I would guess the fins help regulate the heat (and if they're not doing that then it's a cool marking look). For the average rider I would assume all heat needs to be removed as they need to work cold.

I'm not sure what brake fade is with MTB's as I have not used disc (like I mentioned). Is it really the fluid that cannot cope or is it really the pads and discs going higher than it was designed for and so looses it range of friction, perhaps start to glaze over and melt ? (I've melted Canti pads before, literally).
If it is the fluid, then you have the wrong choice of fluid and you're doing something it was not designed for.

Unlike F1 cars which are designed to be run in a narrow range of temperature to get that 'ultimate' response, MTB discs have a wide range to deal with.


Though be good to hear from somebody that has used them and their riding style, but I doubt you could 'test' for them.

 

[mattr]

Yup, it's pretty clear you don't use discs........

Typical operating temps are between not very warm and hot enough to blue the steel of the disc. So maybe 50-80 degrees minimum, up to maybe 300-350. Glazing is something else altogether.

 

[FluffyChicken]

Yup, it's pretty clear you don't use discs........

Typical operating temps are between not very warm and hot enough to blue the steel of the disc. So maybe 50-80 degrees minimum, up to maybe 300-350. Glazing is something else altogether.

Under what conditions, average person bumbling around the bridleways and roads, trip in the wet snady moors, trip round a trail centre, technical quick brake dabbing trails, xc/enduro races, downhill competition.

Operating temps are from sub zero onward,depending on the weather.you seem to neglect the fact they only warm up under use which for most my riding would be very little or short sharp bursts end the end of hills.

I know the principles and have seen and fitted them, just choose not to use them.

There are also different pads designed to work at different temps, styles and usage. Just as these is in canti's pads.
People seem to neglect that when they complain about such things.


Have you used these pads and do they make a difference, are they a different compound?

 

[mattr]

They warm up really really fast. At least the interface between the pad and the disc does. And cool down pretty quickly too. Even short sharp stabs at the brakes will get them warm/hot. Its a lot of energy to dissipate, even if you are just scrubbing off a bit of speed.

Brake fade is boiling fluid (usually due to water contamination of the oil in mtbs), glazing is caused by too much heat with inadequately pressure. i.e. dragging the brakes but making no attempt to actually slow down or stop.

The aluminium backed pads I've used are usually the xc suitable compound, so not much use for anything other than racing.

 

[02gf74]

One cause of brake fade is fluid boiling. Dot type fluid has higher boiling point than mineral oil (shimano, magura) but tends to absorb moisture so that reduces its b.p. (although the brake master cyliner is vented, the hole is so small that i reckon it woukd tame a while for enough water to absorbed before there is any noticeable effect)..


Re. Braming, grabbing a handful then releasing as opposed to a prolonged gentle pull should be more effective, as the rotkr gets to a higher temp so heat transfer is more effective.

 

[mattr]

I did say usually
I have boiled a freshly bled brake before now, my own fault for using an xc brake some way beyond its real design envelope! But 9 times out of 10, fade is caused by ancient oil. (And the air hole in the master cylinder goes to the wrong side of the diaphragm to let water in to the oil.)

 

[syncrosfan]

I think XTR brake pads have a Titanium back plate carrier. Almost as light as Aluminum and they are the worst conductors of heat compared to aluminum or steel. Pretty much the best material for the job. (light, corrosion proof, stand up to high temps, decent heat isolation). No idea how well those work, I use Maguras so the carrier has to be steel...